Transmitter



May 27 '1924.

l. w. BRAY ET.AL

TRANSMITTER nvenTors, [Rv/Nc MBRAY. f''fa Z". BRo/vso/v.

Filed Oct. 25. 1920 Patented May 27, 1924.

UNITED STATES IRVING- W. BRAY AND FRED E. BRQNSON,

or READING, MASSACHUSETTS, Assrenons .To snoer:` PHONE MANUFACTURING cor/rrANY, orv READING, MASSACHUSETTS, A

vCOR1?ORATION 0F MASSACHUSETTS.

TRANSMITTER.

Applicationled October 25, 1920. Serial No. 419,430.

T all whom, t may conce/m Be it known that we, IRVING lV. BRAY and F RED E. BRONSON, citizens of the United- States, and residents of Reading, in the county of Middlesex and State of Massachusetts, have invented an Improvement in Transmitters,'of which the vfollowing description, in connectionwith the accompanying drawings, is a specification, like letters on the drawings representing like parts.

Our present invention is an improved construction of sound transmitters, specially adapted for use in telephones and hearing aid instruments.

The object of the invention is to improve and perfect transmitters and particularly to improve the extremely delicate and sensitive transmitters designed primarily as aids to the hearing of deaf people. Our present invention is directed mainly to the construction of such transmitters, intended to be used with telephones as hearing aids, and we have provided a novel construction which greatly increases the clearness of the sound transmitting as well as producing a desirable amplification of the sound waves, without the objectionable features of prior devices.

In carrying out our invention we prefer to employ a novel type of electrodes, utilizing metallic members therefor, preferably employing electrodes of silver, or silver plate. We have discovered that this feature is of special and peculiar importance in increasing the clearness and distinctness of the sound waves transmitted, while eliminating objectionable noises and outside disturbances. Our improved transmitter has the further advantages of simplicity of construction.l cheapness of manufacture, and permanence in its serviceability. The metallic electrodes seem to result in producing a sensitive silver tone to the sounds transmitted, and aid very materially in the action of the transmitter as a microphone for hearing aids. Y

Referring to the drawings, illustrating preferred embodiments of our invention,

Fig. 1 is a cross-sectional view on the line 1 1 of Fig. 2, of a transmitter embodying our invention; y

Fig. 2 is a plan view shown with the cap and diaphragm partly broken away;

Fig. 3 is a cross-sectional view of the metal ring we employ, f

Fig. 4 is aside viewfof the ring shown in Fig. 3; 1

Fig. 5 is a side and plan view of one of the electrodes; A'

Fig. 6 is a similar side and plan view of a metallicelectrode with` varying formsl of cells; and f 1 Fig. 7 illustrates aA still further modified form of cell in the metallic electrodes.

As shown in the drawings, the transmitter comprises the usual hard'rubber or suitable case 1, to which is secured the cap 2 by the interlocking threaded flanged portions as is usual and as clearly shown in Fig. 1. Through the face of the cap 2 are a' plurality of openings 7 to permit the free ingress and egress of sound and air waves. Within the case is fitted a frame 4, preferably resting upon shoulders 14 on the case 1, see Fig. f

1, which frame has also shoulders 15, to receive and support a metallic ring 3, which ring carries and supports the diaphragm 5.

Attached to the frame 4 centrally thereof and concentrically with the case, is an electrode 6, held by an attaching screw 8 bearing upon an insulating washer 11, said screw fitted into a correspondingly tapped recess in the central part of the frame 4. Preferably, also, vwe fit an insulating washer 9 under the electrode 6, and between the washer 9 and electrode 6 is applied the connecting lug 10, to which one of the current wires may be secured.

We prefer to form the electrode 6 of silver or metal with a silver plating, and also to recess the face of this electrode, at a plurality of points, asindicated at 20, 20, Figs. 1 and 2. This ,construction is substantially that as shown -in detail in Fig. l5, the central recess 21 being that which receives the washer 11 and head of the retaining screw 8.

This silver or silver plated electrode in the center, increases the amount of current passing through it, by decreasing the resistance of the electrode and also decreasing the contact resistance of the carbon granules in the cell, when agitated under the varying pressure exerted by the diaphragm. It will be noted that the diaphragm 5 is closely covering the recesses 20, which latter are filled with carbon as is customary, and thel vibrad?) am tion of the diaphragm thus produces a vmicrophone effect on the current, and conse'- quently' ampliies the sound.Y waves trans mitted thereby.

We find that varying forms and shapes of therecesses in the electrode are benelicial and in Fig'.v 6 the electrode 16 is shown pro` vided with a plurality of recesses 22 of substantially conical form. `In Fig. 7 Wefhave shown the electrode 26 with the recesses 23 therein of a still different form, which receives the carbon granules and eects a beneicial action upon the current and contact resistance. It will also'be appreciated that the ring 3 holds the diaphragm 5 {irmly in contact with the carbon granules in the recesses of the electrode, this being e`ected by the clamping action of the cap 2 thereon in its threaded union with theV casel 1.

It will be appreciated that our improved construction is simple, efficient and economi cal and in use we 'nd that the silver or silveredelectrode is highly beneficial, while the extreme' sensitiveness of thetransmitter is preserved and increased, rendering the 4same suitable for use in hearing aids.

a clamping ring holding said diaphragm in 35 adjusted position and a transmitter cap screwing onto the casing and. forcing.` the clamping. ring onto said` diaphragm.

In testimony whereof, we have signed our names to this specification.

IRVING W. BRAY; :FRED` E. BRONSON.' 

